- #1
gowtham
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How to Calculate maximum torque a riveted joint can stand
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Discussion Overview
The discussion revolves around calculating the maximum torque that a riveted joint can withstand without loosening. Participants explore the mechanics of rivets, the role of friction, and the effects of installation methods, focusing on theoretical and practical considerations in mechanical engineering.
Discussion Character
- Technical explanation
- Debate/contested
- Exploratory
Main Points Raised
- Some participants suggest that the maximum torque depends on the attachment quality between the rivet and the plate, proposing basic equations for torque and force calculations.
- There is a question regarding the application of torque and the axis about which it is applied, with requests for clarification through diagrams.
- Some participants express concern that applying torque about the rivet axis may lead to the rivet spinning in its hole, raising questions about the nature of the friction involved.
- One participant notes that the clamping force is limited by the plastic deformation of the materials involved, suggesting that the coefficient of friction and contact area can be used to determine sliding force.
- Another participant emphasizes the complexity of the problem, indicating that the distribution of clamping force over the contact zone is crucial for calculating maximum torque capability.
- There is a suggestion to improve the joint design by incorporating positive keying to better handle torque loads, rather than relying solely on the rivet.
Areas of Agreement / Disagreement
Participants express multiple competing views regarding the mechanics of the riveted joint and the factors influencing maximum torque. The discussion remains unresolved, with no consensus on the best approach or calculations.
Contextual Notes
Limitations include the lack of specific material characteristics, installation details, and the variability in clamping force distribution, which complicates the analysis of the joint's performance.
- #2
lekh2003
Gold Member
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It depends on how hard rivet and plate are attached together. If you know that, then this is a simple torque/force question which you can solve with some basic equations.gowtham said:
- #3
gowtham
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You mean riveting load?
- #4
russ_watters
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This is unclear to me; where is the torque applied and about which axis? Can you draw it?
- #5
JBA
Science Advisor
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A better view of the rivet's location an orientation would help,as well.
- #6
gowtham
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The torque is applied about the rivet axis!
- #7
- #8
russ_watters
Mentor
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Wouldn't that mean the rivet just spins in its hole?gowtham said:
- #9
Dr.D
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russ_watters said:
I think the question is largely one of friction torque, and that is something that will be very hard to determine without knowing the details of how the rivet was originally installed.
- #10
gowtham
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- 0
Of course the rivet spin in its hole,But there might be some force involved, above only which it will start spinning. Assuming that force as frictional force.How do we proceed with it?russ_watters said:
- #11
gowtham
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The rivet is actually installed using an air hammer.gowtham said:
- #12
Tom.G
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From a non-mechanical guy: It seems the clamping force between rivet and disk will be limited by the plastic deformation limit of either the mating surfaces or the rivet shank. Knowing that, and the contact area between the rivet head(s) and the disc, you can find the maximum clamping force. Then use the coefficient of friction between the two components, the clamping force, and the contact area to find the sliding force.
Note that this will give the maximum, ideal, sliding force. A generous safety factor should be included to cover non-ideal manufacturing and contaminents in the joint.
As an improvement, there could be radial grooves in which ever is the harder material of the joint (or maybe in both). This will add a material shear restraint to the frictional restraint.
That's a starting point anyhow. Since there were no material characterisitcs or assembly procedures given, I doubt much else can be said at this point.
Note that this will give the maximum, ideal, sliding force. A generous safety factor should be included to cover non-ideal manufacturing and contaminents in the joint.
As an improvement, there could be radial grooves in which ever is the harder material of the joint (or maybe in both). This will add a material shear restraint to the frictional restraint.
That's a starting point anyhow. Since there were no material characterisitcs or assembly procedures given, I doubt much else can be said at this point.
- #13
lekh2003
Gold Member
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The simple problem here is that OP has not given any specifications or extra details besides the diagram.
- #14
- #15
Dr.D
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Tom.G said:
It is actually more complicated than this. Knowing the maximum clamping force does little good; what is needed is the detailed distribution of the clamping force over the contact zone. Then the maximum moment capability of that distributed force can be computed. This is all rather theoretical and the actual distribution is virtually unknowable. It probably varies from one rivet installation to the next, because it depends upon the details of the driving event (how hard it is hit, how squarely it is hit, etc).
In short, a single rivet is a lousy way to support a torque!
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